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Unformatted text preview: Lecture 2 Material Covered in This Lecture: * Chapter 1, Section 1.2: Describing Distributions with Numbers. A brief description of a distribution should include its shape and numbers describing its center and spread. Shape: Histogram or Stemplot. Center ? Spread ? 1 1. Measuring center Example1 (Example 1.12, Table1.10): Fuel consumption (miles per gallon) of two-seater cars. 17 20 20 17 18 12 11 10 17 60 9 9 15 12 22 16 13 20 20 15 26 Example1 (continued): Calculate the mean of the fuel consumption data. Question: How about if we remove 60 from the data set? The Honda insight is a hybrid gas electric car that does not belong in the same category as the 20 gasoline powered two seater cars. If we exclude the Insight ,the mean city mileage drops. Note : This shows that the mean is sensitive to the influence of a few extreme observations. These may be outliers, but a skewed distribution that has no outliers will also put the mean toward its long tail. Because the mean cannot resist the influence of extreme observations, we say that it is not a resistant measure of center.influence of extreme observations, we say that it is not a resistant measure of center....
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- Summer '08